Laurel

Ohmmeter for Resistance in Ohms High accuracy & high speed for production environments

(plus transmitter & control outputs)
Description
The Laureate™ Ohmmeter is ideal for high-speed, high-accuracy resistance measurements in a production environment, such as contact resistance measurements. It is factory calibrated for five jumper selectable resistance ranges from 20 Ω to 200 kΩ.and 2.0000 MΩ resistance range with factory modification, with1 mΩ resolution on 20 Ω scale Meter connections can be via 2, 3 or 4 wires. With 4-wire hookup, 2 wires are used for excitation and two separate wires are used to sense the voltage across the resistance to be measured, thereby eliminating any lead resistance effects. With 3-wire hookup, the meter senses the combined voltage drop across the resistance to be measured plus two excitation leads. It also senses the voltage drop across one excitation lead, and then subtracts twice this voltage from the combined total. This technique effectively subtracts lead resistance if the excitation leads are the same.

All resistance ranges are digitally calibrated at the factory, with calibration factors stored in EEPROM on the signal conditioner board. This allows ranges and signal conditioner boards to be changed in the field without recalibrating the meter. If desired, the meter can easily be calibrated using external standards plus scale and offset in software.
High read rates at up to 60 or 50 conversions per second while integrating the signal over a full power cycle are provided by Concurrent Slope (US Pat 5,262,780) analog-to-digital conversion. High read rates are ideal for high-throughput manufacturing processes. Peak and valley values are automatically captured and may be displayed via a front panel pushbutton command or a control signal at the rear connector, or be transmitted as serial data.

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Designed for system use
Optional plug-in boards for communications and control include Ethernet and other serial communication boards, dual or quad relay boards, and anisolated analog output board. Laureates may be powered from 85-264 Vac or optionally from 12-32 Vac or 10-48 Vdc. The display is available with red or green LEDs. The 1/8 DIN case meets NEMA 4X (IP65) specifications from the front when panel mounted. Any setup functions and front panel keys can be locked out for simplified usage and security. All power and signal connections are via UL / VDE / CSA rated screw clamp plugs.
Multiple relay operating modes
Multiple relay operating modes are selectable in software. One of these is band deviation setpoint operation, where a deviation limit (such as 50 counts) is set up around both sides of the setpoint. The relay closes (or opens) when the reading falls within the deviation band, and opens (or closes) when the reading falls outside of this band. This mode sets up a passband around the setpoint and is often used for component testing.

Specifications

Display
Readout 5 digits, 7-segment, 14.2 mm (.56")
Color Red or green LED
Indicators 2 red LED lamps
Accuracy
Accuracy at 25°C ±0.01% of range ± 2 counts
Span tempco ±0.003% of reading/°C
Electrical
Connection 2, 3 or 4-wire
Max applied voltage 100 mV
Overvoltage protection 125 Vac
Open sensor indication Flashes full-scale
A-to-D Conversion
Technique Concurrent Slope™ (Pat 5,262,780)
A-to-D Rate 60/s at 60 Hz, 50/s at 50 H
Output Update 56/s at 60 Hz, 47/s at 50 Hz
Display Update 3.5/s at 60 Hz, 3/s at 50 Hz
Power
Voltage, standard 85-264 Vac or 90-300 Vdc (DC operation not UL approved)
Voltage, optional 12-32 Vac or 10-48 Vdc
Frequency DC or 47-63 Hz
Power Isolation 250V rms working, 2.3 kV rms per 1 min test
Analog Output (standard)
Output Levels 4-20 mA, 0-20 mA, 0-10V, -10 to +10V (jumper selectable)
Current compliance 2 mA at 10V ( > 5 kOhm load)
Voltage compliance 12V at 20 mA ( < 600 Ohm load)
Scaling Zero and full scale adjustable from -99999 to +99999
Resolution 16 bits (0.0015% of full scale)
Isolation 250V rms working, 2.3 kV rms per 1 min test
Relay Outputs (optional)
Relay Types 2 Form C contact relays or 4 Form A contact relays (NO) 2 or 4 Form A, AC/DC solid state relays (NO)
8A at 250 Vac or 24 Vdc for contact relays
Current Ratings 130 mA at 140 Vac or 180 Vdc for solid state relays
Output common Isolated commons for dual relays or each pair of quad relays
Isolation 250V rms working, 2.3 kV rms per 1 min test
Serial Data I/O (Optional)
Board Selections EthernetEthernet-to-RS485 serverUSBUSB-to-RS485 serverRS485(dual RJ11), RS485 Modbus (dual RJ45), RS232.
Protocols Modbus RTU, Modbus ASCII, Laurel ASCII protocol
Data Rates 300 to 19200 baud
Digital Addresses 247 (Modbus), 31 (Laurel ASCII),
Isolation 250V rms working, 2.3 kV rms per 1 min test
Environmental
Operating Temp. 0°C to 60°C
Storage Temp. -40°C to 85°C
Relative Humidity 95% at 40°C, non-condensing
Protection NEMA-4X (IP-65) when panel mounted

Resistance Measurement with Excitation & Lead Compensation

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Ohmmeter hookup
Ohmmeter hookup can be via 2, 3 or 4 wires to the J5 connector. The meter applies a fixed excitation current for each resistance range.
In 4-wire hookup, different pairs of leads are used to apply the excitation current and sense the voltage drop across the unknown resistance, so that the IR drop across the excitation leads is not a factor.
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In 3-wire hookup
In 3-wire hookup, the meter senses the combined voltage drop across the unknown resistance plus two excitation leads. It also senses the voltage drop across one excitation lead, and then subtracts twice this voltage from the combined total. This technique effectively subtracts all lead resistance and compensates for ambient temperature changes if the two excitation leads are identical.
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In 2-wire hookup
In 2-wire hookup,the meter senses the combined voltage drop across the unknown resistance and both lead wires. The voltage drop across the lead wires can be measured by shorting out the resistance during meter setup, and this voltage is then automatically subtracted from the combined total. However, changing resistance of the lead wires due to ambient temperature changes will not be compensated.
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QA Application with Relay Option in Passband Mode
A deviation limit (50 mΩ in this example) is set up around both sides of a setpoint. The relay closes (or opens) when the reading falls within the deviation band, and opens (or closes) when the reading falls outside of this band. This mode sets up a passband around the setpoint and can be used for contact resistance testing.
Purchase
5672 Bolsa Avenue Huntington Beach, CA 92649 - USA - Ph (714) 622-2000 - Fax (714) 622-2001